The present invention relates to a device which can be used in association with a tubing hanger and to a tubing hanger system which can be adjusted to tension a tubular string or casing string which is connected to a subsea wellhead without the need to pull the tubing hanger.
A tubular string is generally required in offshore petroleum production installations to provide a fluid conduit between a subsea wellhead and a surface wellhead located on an offshore drilling or completion rig. An adjustable tubing hanger is typically used to space out the tubular string between the subsea wellhead and the surface wellhead.
Most commonly in the practice, adjustable mandrel-type tubing hangers have been used but the require that to make the adjustment of the tension on the tubing string, the tubing hanger must be pulled, and then reinstalled for the correct tension on the tubular string.
Adjustable tubing hangers are known in the art, see U.S. Pat. Nos. 6,065,542, 5,878,816, and 5,653,289. In U.S. Pat. No. 6,065,542, an adjustable casing hanger has a body suspended within a wellhead that comprises a casing head attached to an offshore rig, and a tubing head connected to the casing head by a suitable connector. A threaded coupling connects the lower end of the casing hanger body to the upper end of a tieback casing string, which in turn is connected to a subsea wellhead. A plurality of grooves is on the outer surface of the upper part of the casing hanger body. The grooves extend from the upper end of the casing hanger body to a point above the lower end of the casing hanger body. The grooves define ridges on the outer diameter surface of the casing hanger body portion, which among other functions helps to center the casing hanger within the wellhead, but are not for tensioning the casing string. Various slots extend below the grooves for communicating fluid between the casing hanger and the wellhead to an annulus port in the wellhead. The adjustability features of this patent have lacked the secure interlocking features which has been long needed. The other two patents are variations on this construction.
The problems with the known systems are that either the whole system has to be pulled out of the wellhead in order to adjust the system or the adjustments are made with complicated mechanisms. A need has long existed to be able to adjust a tubing hanger by simply running in a pin to tighten or loosen tension. A need has long existed for a means to adjust tensioning on a tubular string without having to overpull the entire assembly. A need has long existed for an adjustable tubing hanger assembly which only uses the minimum of overpull for adjusting tension on the tubular string.
The present invention is directed at an adjustable tubing hanger which meets these long felt needs. The invention enables a tubing hanger to be adjusted and readjusted without the need for pulling the entire tubing hanger to adjust tension on the tubular string.
The present invention relates to an adjustable tubing hanger assembly, a tubing hanger system which includes an adjustable tubing hanger assembly and a method for installing and using an adjustable tubing hanger assembly to adjust tension on the tubular string used in a tubing hanger without the need to raise the tubing hanger or a blow out preventer (BOP) stack.
The present invention contemplates an adjustable tubing hanger assembly for suspending a tubular string from a wellhead comprising: a upper body having a seal; a lower body attached to the upper body and the tubular string; a carrier assembly located between the upper body and the lower body providing at least one metal seal for the annulus; a drive lock assembly attached to the lower body comprising: a tension lock; a plurality of segments, each segment having an outer diameter with a grooved profile forming a load bearing interlock for the drive lock assembly; and wherein the tension on the tubular string is adjustable depending on adjustments made to the interlock position of the grooved profile.
The present invention also relates to an adjustable tubing hanger system for suspending a tubular string from a wellhead comprising: a tubing hanger; an adjustable tubing hanger assembly disposed adjacent the tubing hanger wherein the adjustable tubing hanger assembly comprises: an upper body having a seal; a lower body attached to the upper body; a carrier assembly located between the upper body and lower body providing at least one metal seal for the annulus; a drive lock assembly attached to the lower body comprising a tension lock and a grooved profile forming an interlock with the drive lock assembly; and wherein the tension on the tubular string is adjustable depending on adjustments made to the interlock position of the grooved profile.
The present invention further relates to a method for adjusting and readjusting a tubing hanger having a tubular string connected to a well, comprising: connecting a retrieving tool having a stab in profile to stab into an adjustable tubing hanger assembly; adjusting tension on the tubular string to hold the tubular string vertical; analyzing the alignment of the tubular string and if the alignment requires adjusting, then releasing tension using the tensioning pin; readjusting the tubular string using the retrieving tool; and activating the drive lock to maintain tension on the tubular string.
These and other objects and advantages of the present invention will be made apparent from the following detailed description, with reference to the accompanying drawing.